There are DC-DC converters which generate a desired level of DC voltage by converting an externally input DC voltage into a high-frequency AC voltage and smoothing the AC voltage and output the DC voltage to a subsequent circuit. A plurality of DC-DC converters of this type are mounted in, e.g., an electronic device such as a cellular phone handset which uses a battery as its power source and generate a plurality of voltages for respective functional blocks.
In recent years, the operating frequencies of DC-DC converters have been increasing to cope with the lower voltage and higher current of a power source. For this reason, high-speed operation and high efficiency are required of a control circuit of a DC-DC converter. However, implementation of high-speed operation involves problems such as an increase in current consumption and an increase in circuit scale.